JP2012192618A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve a problem that an unstable pressure of a head causes fluid dripping or bubble sucking to generate discharge failure at the exhaust from a plurality of head tanks simultaneously.SOLUTION: An exhaust unit 200 includes: an exhaust chamber 105 in which exhaust ports 111 of a plurality of ink chambers 104 are open; an atmosphere opening valve 80 that opens and closes the exhaust ports 111 of the plurality of ink chambers 104 simultaneously; a drive lever 82 and a drive pin 83 that open and close the atmosphere opening valve 80; a pin drive chamber 85 of which part of wall surface is formed by a flexible film 86 having the drive pin 83 and that communicates with an exhaust tube 112; and a choke channel 89 that communicates between the exhaust chamber 105 and the pin drive chamber 85. While liquid is in the choke channel 89, an exhaust pump 60 sucks an exhaust channel 88 to contract a volume of the pin drive chamber 85, and thereby the atmosphere opening valve 80 opens the exhaust ports 111.

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus provided with a recording head for discharging droplets.

  As an image forming apparatus such as a printer, a facsimile machine, a copying apparatus, a plotter, and a complex machine of these, for example, an ink jet recording apparatus is known as an image forming apparatus of a liquid discharge recording method using a recording head for discharging ink droplets. . This liquid discharge recording type image forming apparatus ejects ink droplets from a recording head onto a conveyed paper to form an image (recording, printing, printing, and printing are also used synonymously). Serial type image forming device that forms an image by ejecting droplets while the recording head moves in the main scanning direction, and a line type that forms images by ejecting droplets without the recording head moving There is a line type image forming apparatus using a head.

  In the present application, an “image forming apparatus” is an apparatus that forms an image by landing ink on a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics (simple liquid ejection apparatus) In addition, “image formation” not only gives an image having a meaning such as a character or a figure to a medium but also gives an image having no meaning such as a pattern to the medium. It also means (including what is simply referred to as a droplet discharge device or a liquid discharge device). In addition, the term “ink” is not limited to what is called ink, but is any liquid that can form an image, such as a recording liquid, a fixing liquid, a liquid, a DNA sample, or a patterning material. Used as a general term. The term “paper” is not limited to paper, but includes the above-described OHP sheet, cloth, and the like, and means that ink droplets adhere to the recording medium, recording medium, recording paper, recording It is used as a general term for what includes what is called paper. In addition, the “image” is not limited to a planar image, and includes an image given to a three-dimensionally formed image and an image formed by three-dimensionally modeling a solid itself.

  As a liquid discharge head (droplet discharge head) used as a recording head, a piezoelectric head or the like is used to displace a diaphragm and change the volume in the liquid chamber to increase the pressure to discharge the liquid droplet. There is known a thermal type head in which a heating element that generates heat is provided, the pressure in the liquid chamber is increased by bubbles generated by the heat generation of the heating element, and droplets are discharged.

  In such a liquid ejection type image forming apparatus, it is particularly desired to improve the image forming throughput, that is, to increase the image forming speed. From the large-capacity ink cartridge (main tank) installed on the main body through the tube. Ink is supplied to a head tank (including sub tanks and buffer tanks) above the recording head.

  By the way, when ink is supplied from the ink cartridge to the head tank using a resin tube or the like, it is difficult to always fill the head tank with 100% ink and use an air layer above the head tank. Is formed. The amount of air in the head tank tends to increase over time due to air permeation from the resin tube and the wall surface of the head tank and air bubbles mixed when the ink cartridge is detached.

  Here, there is no particular problem if the amount of air in the head tank is small, but if the amount of air is too large, the amount of volume change of the air with respect to temperature changes increases and is maintained at a negative pressure within a certain range. The head tank internal pressure to be exceeded is out of the allowable range, so that ink oozes out from the nozzle of the head or normal ejection cannot be performed. Further, when there is a large amount of air in the head tank, there is a problem in that air is mixed with the ink in the head, making it impossible to eject droplets.

  Therefore, it is necessary to keep the pressure in the head tank at a constant negative pressure, and at the same time, keep the air from exceeding a predetermined amount.

  Therefore, conventionally, an air storage part that is provided in the middle of a liquid supply channel that supplies liquid to the head and temporarily stores air in the liquid, a valve that opens and closes an exhaust passage from the air storage part to the outside, A flexible member that deforms in response to the pressure in the passage, and the negative member generated in the exhaust passage deforms the flexible member to open the valve, and allows the air in the air reservoir to pass through the exhaust passage. There is known one provided with an exhaust mechanism that discharges to the outside via this (Patent Document 1).

JP 2010102633 A

  However, in the configuration disclosed in Patent Document 1, a flexible member provided in a part of the exhaust passage is deformed by a negative pressure (exhaust pressure) generated in the exhaust passage, so that a valve (valve) is provided. Since it is configured to open, there is a problem that the exhaust pressure when the valve is opened affects the pressure of the head, and air is likely to be caught from the nozzle into the head.

  That is, in order to open the valve, it is necessary to apply a large negative pressure to the exhaust passage. In this case, when the valve is opened, the negative pressure directly acts on the head. In particular, when exhausting from a plurality of air reservoirs at the same time, the required negative pressure is further increased, and it is difficult to exhaust while maintaining the head pressure stably.

  The present invention has been made in view of the above problems, and an object of the present invention is to enable exhaust from a plurality of head tanks at the same time while maintaining a stable head pressure.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
A recording head having nozzles for discharging droplets;
A head tank having a plurality of liquid storage chambers for supplying the liquid to the recording head;
An exhaust means having a discharge path for discharging air from the head tank;
A suction means connected to the discharge path,
The exhaust means includes
An exhaust chamber in which exhaust ports of the plurality of liquid storage chambers are opened;
A valve member for simultaneously opening and closing the exhaust ports of the plurality of liquid storage chambers;
A valve drive member for opening and closing the valve member;
A valve drive chamber in which a part of the wall surface is formed of a flexible member provided with the valve drive member and communicates with the discharge path;
A choke flow path communicating the exhaust chamber and the valve drive chamber;
The valve member opens the exhaust port by contracting the volume of the valve drive chamber by sucking the discharge channel with the suction means in a state where liquid is interposed in the choke channel.

  Here, the choke flow path can be configured such that the lower portion of the exhaust chamber and the lower portion of the valve drive chamber are communicated with each other.

  The valve drive chamber may be provided with a biasing means for biasing in the direction of increasing the volume of the valve drive chamber.

  In addition, the liquid storage chamber may include an exhaust adjustment valve that increases the fluid resistance of the exhaust port when the liquid level increases.

  The liquid storage chamber may include a liquid level detecting unit that detects the position of the liquid level.

  Moreover, it can be set as the structure provided with the volume detection means which detects the volume of the said valve drive chamber.

  In this case, when the volume detection means detects that the valve drive chamber has continued to be contracted for a certain period of time, the suction from the discharge channel can be stopped.

  In addition, after the suction from the discharge path is stopped, it is possible to determine that the discharge operation of the air from the head tank is completed when the volume detection unit detects that the volume of the valve drive chamber has expanded.

  According to the image forming apparatus of the present invention, the exhaust means includes an exhaust chamber in which the exhaust ports of the plurality of liquid storage chambers open, a valve member that simultaneously opens and closes the exhaust ports of the plurality of liquid storage chambers, and opens and closes the valve member. A valve driving member, a flexible member provided with the valve driving member, a part of the wall surface of which is formed, a valve driving chamber communicating with the discharge path, and a choke flow path communicating the exhaust chamber and the valve driving chamber And with the liquid interposed in the choke flow path, the valve member opens the exhaust port by sucking the discharge flow path with the suction means and contracting the volume of the valve drive chamber. A plurality of head tanks can be evacuated simultaneously while maintaining a stable head pressure.

1 is a schematic plan view illustrating an ink jet recording apparatus as an image forming apparatus according to an embodiment of the present invention. It is a schematic front explanatory drawing similarly. It is a schematic side surface explanatory drawing similarly. FIG. 2 is an enlarged explanatory view of a main part for explaining a recording head of the same apparatus. It is a plane explanatory view of a head tank in a 1st embodiment of the present invention. It is front explanatory drawing of the head tank. It is side surface explanatory drawing of a discharge part. FIG. 8 is a cross-sectional explanatory view taken along line AA in FIG. 7. FIG. 8 is a cross-sectional explanatory view taken along line BB in FIG. 7. It is front explanatory drawing of the head tank with which it uses for description of exhaust operation by an exhaust part. It is sectional explanatory drawing explaining the state of the exhaust part in exhaust operation | movement. It is sectional explanatory drawing explaining the state of the exhaust part in exhaust operation | movement. It is front explanatory drawing of the head tank in 2nd Embodiment of this invention. It is front explanatory drawing of the head tank in 3rd Embodiment of this invention. It is sectional explanatory drawing with which it uses for description of the exhaust operation of an exhaust part. It is sectional explanatory drawing with which it uses for description of the exhaust operation of an exhaust part.

Embodiments of the present invention will be described below with reference to the accompanying drawings. An ink jet recording apparatus as an image forming apparatus according to an embodiment of the present invention will be described with reference to FIGS. 1 is a schematic plan view of the recording apparatus, FIG. 2 is a schematic front view, and FIG. 3 is a schematic side view.
The ink jet recording apparatus includes a guide rod 122 which is a guide member horizontally mounted on the left and right side plates 123L and 123R provided upright on the main body frame 30, and a guide rail attached to a rear frame 128 which is horizontally mounted on the main body frame 30. 124, the carriage 120 is slidably held in the main scanning direction (guide rod longitudinal direction), and the carriage 120 is moved and scanned in the longitudinal direction (main scanning direction) of the guide rod 122 by a main scanning motor and a timing belt (not shown). To do.

  For example, a recording head 1 including one or a plurality of liquid ejection heads that eject ink droplets of black (K), cyan (C), magenta (M), and yellow (Y) is mounted on the carriage 120. The head 1 has a plurality of ink discharge ports (nozzles) arranged in a direction crossing the main scanning direction, and is mounted with the ink droplet discharge direction facing downward.

  Here, as shown in FIG. 4, the recording head 1 includes a heating element substrate 2 and a liquid chamber forming member 3, and a common flow path 7 and a liquid chamber ( The ink sequentially supplied to the individual flow path) 6 is ejected as droplets. This recording head 1 is a thermal type that obtains a discharge pressure by boiling an ink film by driving a heating element 4, and the direction of ink flow to the discharge energy acting part (heating element part) in the liquid chamber 6 and the nozzles. 5 is a side shooter type configuration in which the central axis of the opening 5 is a right angle.

  As the recording head, there are various methods such as a method in which the diaphragm is deformed by using a piezoelectric element, and the diaphragm is deformed by an electrostatic force to obtain a discharge pressure. The present invention can be applied to such an image forming apparatus.

  On the other hand, below the carriage 120, the paper 8 on which an image is formed by the recording head 1 is conveyed in a direction perpendicular to the main scanning direction (sub-scanning direction). As shown in FIG. 3, the paper 8 is sandwiched between the transport roller 125 and the presser roller 126, transported to the image forming area (printing unit) by the recording head 1, sent onto the printing guide member 128, and discharged. A pair of rollers 127 feeds in the paper discharge direction.

  At this time, the scanning of the carriage 120 in the main scanning direction and the ink ejection from the recording head 1 are synchronized at an appropriate timing based on the image data, and an image for one band is formed on the paper 8. After image formation for one band is completed, a predetermined amount of paper 8 is fed in the sub-scanning direction, and the same recording operation as described above is performed. These operations are repeated to form an image for one page.

  On the other hand, a head tank (buffer tank, sub tank) 101 in which an ink chamber 104 (described later) for temporarily storing ink to be ejected is formed is integrally connected to the upper portion of the recording head 1. Here, “integral” includes that the recording head 1 and the head tank 101 are connected by a tube, a tube, or the like, and both are mounted on the carriage 120 together.

  In the head tank 101, liquid is supplied from an ink cartridge (main tank) 76, which is a liquid tank containing ink of each color that is detachably attached to a cartridge holder or the like provided on one end side in the main scanning direction on the apparatus main body side. Ink of a required color is supplied through the supply tube 16.

  A suction pump 60 is connected to the head tank 101 as a suction means via an exhaust tube 112.

  A maintenance / recovery mechanism 31 that performs maintenance / recovery of the recording head 1 is arranged on the other end side in the main scanning direction of the apparatus main body. The maintenance / recovery mechanism 31 includes a cap 32 for capping the nozzle surface of the recording head 1, a suction pump 34 for sucking the inside of the cap 32, a discharge path 33 for discharging waste liquid of ink sucked by the suction pump 34, and the like. The waste liquid discharged from the discharge path 33 is discharged to a waste liquid tank disposed on the main body frame 30 side. The maintenance / recovery mechanism 31 includes a moving mechanism for moving the cap 32 forward and backward (in this example, ascending and descending) with respect to the nozzle surface of the recording head 1. Further, although not shown, the maintenance / recovery mechanism 31 is provided with a wiper member that wipes the nozzle surface of the recording head 1 by a wiping unit so as to be able to advance and retreat relative to the nozzle surface.

  Next, a first embodiment of the present invention applied to this ink jet recording apparatus will be described with reference to FIGS. 5 is an explanatory plan view of the head tank according to the embodiment, and FIG. 6 is an explanatory front view of the head tank. In addition, in each drawing, in order to help understanding, description of components is omitted as appropriate, or a partial cross-sectional view is used.

  The head tank 101 is an ink chamber 104Y, 104M, 104C, or 104K that is a liquid storage chamber that stores four colors of Y, M, C, and K. "Y, M, C, K" sub-codes are added). Inside the head tank 101, a filter 109 is provided in the vicinity of the connection portion with the recording head 1, and ink that has been filtered to remove foreign matters and the like is supplied to the recording head 1 through the supply port 21.

  Further, a film member 107, which is a flexible member molded in a convex shape, is provided on one wall surface of the head tank 101, and is urged by a spring 108 in the direction of expanding the volume of the head tank 101. In addition, an air amount detection sensor 103 that detects the amount of air in the head tank is provided above the head tank 101.

  Here, the air amount detection sensor 103 has an electrode pair configuration, and detects the ink level in the ink chamber 104 based on a change in electrical resistance between the two electrodes. As described above, one end side of each color liquid supply tube 16 is connected to the head tank 101, and the other end side of each liquid supply tube 16 is connected to the ink cartridge 76. The ink cartridge 76 is disposed below the nozzle surface of the recording head 1 and holds the inside of the recording head 1 at an appropriate negative pressure due to a water head difference.

  A discharge mechanism (discharge unit) 200 that is a discharge unit that discharges the air in each ink chamber 104 through a discharge tube 112 that is a discharge channel is provided on the top of the head tank 101.

  Next, the discharge unit 200 will be described with reference to FIGS. 4 is an enlarged view of part A in FIG. 4. FIG. 7 is an explanatory side view of the discharge part. FIG. 8 is an explanatory sectional view taken along line AA in FIG. It is a section explanatory view which meets a BB line.

  The discharge unit 200 has an exhaust chamber 105 that is common to each ink chamber 104 and has an exhaust port 111 that is an exhaust port provided at the top of each ink chamber 104. The upper portion of the exhaust chamber 105 is closed by a member 106.

  In the exhaust chamber 105, an air release valve 80, which is a valve member that simultaneously opens and closes the exhaust port 111 of each ink chamber 104, is provided. The air release valve 80 is a normally closed valve in which a valve body 80a provided with a part of a seal member 80b is pressed against the opening side of the exhaust port 111 by an urging spring 81 as urging means. The air release valve 80 opens the exhaust port 111 when lifted upward by an L-shaped drive lever 82 disposed below. The drive lever 82 is supported by a support shaft 82a so as to be swingable.

  Further, the exhaust chamber 105 communicates with a lower portion of a pin drive chamber 85 which is a valve drive chamber through an opening (discharge port) 89a in the lower portion thereof via a choke flow path 89. The choke flow path 89 is a thin pipe line, and is formed by closing a groove opening formed in the wall surface of the head tank 101 with a film 86.

  In the pin drive chamber 85, a drive pin 83 that is disposed so as to be movable back and forth with respect to the drive lever 82 and is a valve drive member, and a biasing spring 84 that biases the drive pin 83 away from the drive lever 82. Is provided. The wall surface of the pin drive chamber 85 is also formed of the film 86 which is a flexible member, and the drive pin 83 moves in the direction of pushing the drive lever 82 when the film 86 is deformed inward.

  A through hole through which the drive pin 83 passes is formed between the pin drive chamber 85 and the exhaust chamber 105, but a choke between the pin drive chamber 85 and the exhaust chamber 105 is provided by a deformable seal member 87. A structure other than the flow path 89 does not allow communication.

  The pin drive chamber 85 communicates with the exhaust flow path 88 so that the exhaust pump 60 can suck and exhaust the gas through the exhaust tube 112.

  The exhaust pump 60 is preferably a gear pump, a diaphragm pump, or the like that opens the flow path when stopped. However, even if the flow path is closed when stopped, such as a tube pump, a branch path is provided to open the atmosphere. Any configuration can be used.

  Next, the exhaust operation by the exhaust unit 200 will be described with reference to FIGS. 10 is an explanatory front view of the head tank, and FIGS. 11 and 12 are cross-sectional explanatory views illustrating different states of the exhaust section during the exhaust operation.

  First, as shown in FIG. 10, since the liquid level is lowered by the accumulation of air in the ink chamber 104, the liquid level is lowered to a predetermined height or less by the air amount detection sensor 103, that is, in the ink chamber 104. It is detected that a certain amount or more of air has accumulated.

  Therefore, when exhaust is started by the exhaust pump 60, first, as shown in FIG. 11, since the atmosphere release valve 80 is initially closed, the air in the pin drive chamber 85 is discharged. As a result, when the film 86 is pulled inward, the drive pin 83 is pushed against the biasing force of the biasing spring 84, and as shown in FIG. 12, the drive lever 82 swings in the direction of the arrow, The air release valve 80 is opened. By opening the atmosphere release valve 80, the air in each ink chamber 104 is discharged to the exhaust chamber 105 through the discharge port 111.

  At this time, if the exhaust flow rate is excessively increased, the negative pressure inside the ink chamber 104 increases, and a problem occurs in which air is sucked from the nozzles of the recording head 1. Therefore, the exhaust gas flow rate is preferably about 0.1 to 0.2 cc / s. On the other hand, when the exhaust gas flow rate is small, the negative pressure in the pin drive chamber 85 becomes small, so that the air release valve 80 is closed (FIG. 11). When the air release valve 80 is closed, the negative pressure in the pin drive chamber 85 again increases, so the air release valve 80 is opened and the ink chamber 104 is exhausted. Accordingly, exhaust of the ink chamber 104 proceeds while repeating the state between FIG. 11 and FIG.

  Since the air amount detection sensor 103 is provided in the present embodiment, the exhaust pump 60 can be stopped based on the detection result of the air amount detection sensor 103.

  Here, in the present embodiment, a plurality of ink chambers 104 are connected to one exhaust path (from the discharge port 111 to the exhaust chamber 105, the choke flow path 89, the pin drive chamber 85, the exhaust flow path 88, the discharge tube 112, and the exhaust pump 60. To the exhaust route).

  When this exhaust operation is performed, as shown in FIG. 12, the air release valve 80 is not completely opened, and the valve body 80a is slightly raised, and the exhaust ports 111 of some ink chambers 104 may not be opened. sell. In this case, the ink in the ink chamber 104 that has been exhausted flows out from the exhaust port 111 to the exhaust chamber 105. The ink that has flowed out flows into the choke channel 89. When ink enters the choke flow path 89, the negative pressure in the pin drive chamber 85 increases rapidly, and the push-in amount of the drive pin 83 is maximized to raise the atmosphere release valve 80 completely. As a result, the exhaust ports 111 of all the ink chambers 104 are opened, so that the ink chambers 104 that are not exhausted can be eliminated.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 13 is an explanatory front view of the head tank in the moving embodiment.
In this embodiment, instead of the air amount detection sensor 103 in the first embodiment, a float valve 110 is provided in each ink chamber 104.

  Even in this configuration, when exhaust is performed by driving the exhaust pump 60, exhaust of each ink chamber 104 proceeds while repeating the state between FIGS. 11 and 12 as described above. When the exhaust proceeds and the ink level in the ink chamber 104 rises, the exhaust port 111 is closed by the float valve 110, so that the ink chamber 104 and the exhaust chamber 105 are automatically shut off.

  That is, when the exhaust flow rate is reduced in order not to destroy the negative pressure of the recording head 1, even if the exhaust port 111 of some ink chambers 104 may not open due to the small exhaust flow rate, Since the suction source is blocked by the float valve 110 from the exhausted ink chamber 104, the negative pressure in the pin drive chamber 85 increases each time, and finally the exhaust ports 111 of all the ink chambers 104 are opened. The ink chamber 104 that can be opened and is not exhausted can be eliminated.

Next, a third embodiment of the present invention will be described with reference to FIGS. 14 is a front explanatory view of the head tank in the same embodiment, and FIGS. 15 and 16 are cross-sectional explanatory views showing different states for explaining the exhaust operation of the exhaust section.
In this embodiment, the optical sensor for detecting the position of the drive pin 83 by detecting the displacement of the film 86 which is a flexible member forming the wall surface of the pin drive chamber 85 in the second embodiment. The position detection sensor 91 which consists of is provided.

  That is, as described above, when the air in all the ink chambers 104 is exhausted, the inside of the exhaust path is choked, so that the pin driving chamber 85 is completely contracted as shown in FIG. If the contracted time continues for a certain time or more, it can be determined that the exhaust has been completed, and the exhaust pump 60 can be stopped.

  Thereafter, the volume of the pin drive chamber 85 is recovered mainly by the backflow of fluid (air or ink) from the exhaust pump 60 side, the pressure of the drive lever 82 by the drive pin 83 is weakened, and the air release valve 80 is closed.

  Therefore, since the position detection sensor 91 detects the position of the drive pin 83, it can be confirmed that the atmosphere release valve 80 is closed, so that it is possible to shift to the next operation such as a printing operation without useless waiting time. In the present embodiment, the pin drive chamber 85 is provided with the biasing spring 84 that acts in the direction of expanding the volume, so that the position return of the drive pin 85 when the exhaust pump 60 is stopped can be greatly and reliably performed. Can be.

  In the above description, the operation and effect of the present invention have been described with an example in which different color inks are supplied to a plurality of heads. However, when the same color ink is supplied to a plurality of heads, or not to colors. The same applies to the case where inks having different prescriptions are supplied to a plurality of heads. The present invention can also be applied to a liquid supply system in which different types of liquid are ejected from one head using a head having a plurality of nozzle rows in one head. Further, the present invention is not limited to an image forming apparatus that discharges ink in a narrow sense, and can also be applied to a liquid discharging apparatus that discharges various liquids (included in the “image forming apparatus” in the present invention). .

1 Recording head (liquid ejection head)
16 Liquid supply tube 30 Sub tank 60 Exhaust pump 76 Ink cartridge (main tank: liquid tank)
80 Atmospheric release valve 82 Drive lever 83 Drive pin 85 Pin drive chamber 86 Film (flexible member)
88 Exhaust flow path 89 Choke flow path 104 Ink chamber (liquid storage chamber)
105 Exhaust chamber 111 Exhaust port (exhaust port)
112 discharge tube 120 carriage 200 discharge section (discharge mechanism, discharge means)

Claims (8)

A recording head having nozzles for discharging droplets;
A head tank having a plurality of liquid storage chambers for supplying the liquid to the recording head;
An exhaust means having a discharge path for discharging air from the head tank;
A suction means connected to the discharge path,
The exhaust means includes
An exhaust chamber in which exhaust ports of the plurality of liquid storage chambers are opened;
A valve member for simultaneously opening and closing the exhaust ports of the plurality of liquid storage chambers;
A valve drive member for opening and closing the valve member;
A valve drive chamber in which a part of the wall surface is formed of a flexible member provided with the valve drive member and communicates with the discharge path;
A choke flow path communicating the exhaust chamber and the valve drive chamber;
The valve member opens the exhaust port by contracting the volume of the valve drive chamber by sucking the discharge channel with the suction means in a state where liquid is interposed in the choke channel. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the choke channel communicates a lower portion of the exhaust chamber and a lower portion of the valve drive chamber.   The image forming apparatus according to claim 1, wherein the valve driving chamber is provided with a biasing unit that biases the valve driving chamber in a direction of increasing a volume of the valve driving chamber.   4. The image forming apparatus according to claim 1, wherein the liquid storage chamber includes an exhaust adjustment valve that increases a fluid resistance of the exhaust port by increasing a liquid level. 5.   5. The image forming apparatus according to claim 1, wherein the liquid storage chamber includes a liquid level detection unit that detects a position of the liquid level.   The image forming apparatus according to claim 1, further comprising a volume detection unit that detects a volume of the valve drive chamber.   The image forming apparatus according to claim 6, wherein when the volume detection unit detects that the valve driving chamber has continued to be in a contracted state for a certain time, suction from the discharge channel is stopped.   After the suction from the discharge path is stopped, it is determined that the discharge operation of the air from the head tank is completed when the volume detection unit detects that the volume of the valve drive chamber has expanded. Item 8. The image forming apparatus according to Item 7.

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